For a few decades, conventional treatment of abdominal aortic aneurysms (AAA) was limited either to a sit-and-wait strategy, or in cases with too high a risk for aneurysm rupture, a surgical operation using vascular grafts introduced in major open abdominal surgery.
While long term clinical results of the surgical approach were favorable and the treated patients did not need frequent follow-ups, nevertheless the short-term morbidity, including complication rate, hospitalization time, out-of-work period and related expenses warranted continued search for a less invasive, but still definitive, solution of the problem.
Numerous attempts have been made to introduce such definitive treatments to AAA that involve less morbidity, a shorter hospitalization period and lower related costs, and enable the patient to return to routine life sooner. These initiatives resulted in various endovascular stent-grafts that are commercially available or are being clinically and pre-clinically evaluated. A major advantage in these newer devices is that their implantation involves a significantly less invasive procedure, including creating an endovascular working channel—usually via an incision in the groin area—to the diseased abdominal aorta, through which a self expandable stent-graft is typically introduced. In most cases, a bifurcated device is employed, either in one piece, or in some cases, smaller caliber iliac-grafts are deployed subsequently after the main aortic devices have been well positioned.
Nonetheless, the relatively new endovascular approach has its share of problems and limitations. Some of the major outstanding problems include:                The implantation is complicated because most AAA stent grafts are implanted via two working channels, one in each side of the groin. The interventional radiologist typically has to introduce one main piece of the device via one working channel and an extension piece through the other side in a non trivial manner.        There is a prolonged implantation procedure caused by a difficulty to correctly position the stent-graft and the inability to correct its position once deployed, usually due to barbs that penetrate the aortic wall and anchor the graft thereto. This also involves relatively high doses of X-ray radiation, to which the patient and the staff are exposed during the prolonged endovascular procedure.        In earlier AAA stent grafts, device migration was a major issue, sometimes leading to obstruction of blood flow into the neighboring renal arteries or in other cases exposing the aneurysm to renewed blood penetration. Conventional AAA stent-grafts were typically prone to migration since they are essentially built along a single longitudinal axis and they may migrate along the same axis.        Endovascular leaks (in short—endoleaks) are another problem. Two types of endoleaks are defined: A type I endoleak is leakage of blood around the stent-graft and into the aneurismal sac, which may lead to rupturing the aneurysm. A Type II endoleak occurs when blood/plasma leaks through the graft wall and into the aneurismal space. Type II endoleaks have been mostly resolved by the introduction of finer-woven graft fabrics, performing pre-clotting procedures and/or incorporation of collagen or other procoagulation materials into the graft wall. Type I endoleaks are nonetheless more difficult to prevent and treat.        The device cost is very high. Current self-expandable AAA stent-grafts are usually bifurcated grafts, one piece or multi-piece devices. The connection with the graft fabric is typically achieved by hand stitching to a metallic, self-expandable frame. Hand labor related issues together with the critical QA/QC standards with which these devices have to comply make these devices quite expensive to manufacture.        There are the necessary follow-ups which are time consuming.        